Case study

CatCard: replacement firmware built around Coldcard bootloader contracts

CatCard implements Rust replacement firmware for Coldcard mk3, mk4, mk5 and Q1 hardware. It documents the protected bootloader's image layout, signature and callgate ABI, then builds board-specific wallet, storage and USB components against those fixed interfaces. The author reports that device builds run, while signing and several transports remain without end-to-end device exercise.

Targets: Firmware
Category: Independent reconstruction cases
Relationship: Independent reconstruction project
Sources reviewed: 2026-11-08

Stars: 15
Last commit: 2026-10-17
Language: Rust
License (GitHub): MIT

GitHub data as of 2026-11-09

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Requirements & limits

Prerequisites: Coldcard mk3, mk4, mk5 or Q1 hardware; firmware images use the bootloader's published developer signing key.
Testing evidence: The author states the firmware is not ready to hold funds; signing, multisig, QR and NFC have not been exercised end to end on a device.
License: MIT License.

Cite

BibTeX

@misc{catcard-coldcard-firmware-case,
  title = {{CatCard: replacement firmware built around Coldcard bootloader contracts}},
  howpublished = {\url{https://github.com/TibaneLabs/catcard}},
  url = {https://github.com/TibaneLabs/catcard},
  urldate = {2026-11-08},
  note = {Awesome REA entry: \url{https://awesomerea.org/resources/catcard-coldcard-firmware-case/}}
}

Plain text

CatCard: replacement firmware built around Coldcard bootloader contracts. https://github.com/TibaneLabs/catcard (accessed 2026-11-08). Awesome REA entry: https://awesomerea.org/resources/catcard-coldcard-firmware-case/

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About this entry

The description was reviewed against primary sources.

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Primary sources

docs/ARCHITECTURE.md GitHub · TibaneLabs/catcard · Revision 038c37c
README.md GitHub · TibaneLabs/catcard · Revision 038c37c
LICENSE GitHub · TibaneLabs/catcard · Revision 038c37c